Method of reducing the alkali solubility of wool by treatment with acrolein



FIPSSO? METHOD OF REDUCING THE ALKALI SOLU- BILITY OF WOOL BY TREATMENT WITH ACROLEIN George Thomson, Milton, Carter G. Cook, Norwood, and Phyllis M. Pepin, Hyde Park, Mass assignors to Fabric Research Laboratories, Inc., Boston, Mass., a corporation of Massachusetts No Drawing. Application July 15, 1953 Serial No. 368,226

4 Claims. (Cl. 8-133) I The present invention relates to the treatment of wool and other keratinous materials, and consists in a process for counteracting the effects of chemical degradation of such materials.

Chemical degradation of wool is caused by many of the treatments to which it is subjected during its processing, particularly treatments under acidic, oxidizing, or reducing conditions, and results in an impairment of the physical or mechanical properties of the wool. During carbonization, for instance, wool is treated with sulfuric acid and baked to remove foreign vegetable matter, and acid conditions are also frequently en.- countered during dyeing, and during decolorizing processes such as the electrolytic stripping process disclosed in US. Patent No. 2,549,099. Such treatments under acidic conditions result in acid damage to the wool, believed to be caused by the hydrolysis, and consequent breaking, of peptide links present in the wool molecule.

Decolorizing and bleaching treatments subject the wool to oxidizing or reducing conditions that also result in degradation of the wool, believed to be caused by the breakage of cystine links in the molecular structure.

The degree of degradation is commonly measured by the alkali solubility, which is increased by degradation. The alkali solubility values used in this disclosure were obtained by immersing a 1 gram sample of the wool in 100 cc. of a 0.1 N aqueous sodium hydroxide solution at a temperature of 65 C. for one hour, then filtering out the wool, rinsing it thoroughly with water and drying. The loss of weight expressed as a percentage of the original weight is the alkali solubility value, and is a generally accepted index to the degree of degradation.

The effect of various degradation-causing treatments of samples of virgin Australian wool and of samples of a commercial blue-dyed yarn are shown in Table I.

TABLE I Alkali Sample Solubility,

Percent 1. New Virgin Australian Raw W 13. 1 2. Sample 1 after boiling for 1 hr. in 0.1 N HCl 45. 2 3. Sample 1 after bleach in commercial 6% H2O; for 16 hr.

at 65 0 39. 6 4. Sample 3 after boiling for 1 hr. in 0.1 N HCl 67.0 5. A commercial blue-dyed wool yarn 11. 8 6. Sample after electrolytic strip in 5% sulfuric acid s u tion (a reducing treatment), as described in U. S. Patent No. 2,549,099 69. 2

The present invention provides a process for treating wool, and other keratinous materials, to enhance its resistance to degradation or to recondition wool that has been damaged, and is effective in counteracting the 1 See Von Bergen and ltlauersberger, American Wool Handbco9lg12nd ed. (1948) (Textile Book Publishers, Inc., N.Y.). p.

Patented Mar. 31, 1959 damaging effects of treatments under acidic, oxidizing, or reducing conditions.

ice

The process of this invention consists essentially in The treatment may be carried out efiectively in solutions containing as little as 0.3 percent by weight of acrolein, but higher concentrations in the range of about 3 to about 6 percent by weight of acrolein are preferred, as they produce better results at a faster rate. Higher concentrations of acrolein are also entirely satisfactory, but unnecessary, for no significant additional improvements in the treatment have been found to result from increasing the acrolein concentration above about 6 percent. The treating solution is preferably neutral or slightly acid, and is accordingly adjusted to have a pH in the range of about 27.

The treatment may be carried out at ordinary temperatures between the freezing point and boiling point of the solution, or at even such higher temperatures as are not destructive to the keratinous materials if pressure systems are to be used. When wool is treated in accordance with this invention to repair damage previously caused by overbleaching, a treatment at a temperature above 65 C. is more efiective than lower temperatures to stabilize the wool against subsequent acid damage, and such higher temperatures are accordingly preferred for this type of treatment.

The time required for the treatment is interrelated with the temperature and concentration, but under the preferred conditions the treatment is ordinarily complete in less than 2 hours, and about 20 minutes is generally adequate. It will be understood, however, in accordance with well known principles of chemical kinetics, that longer or shorter periods of time may be preferred under some conditions depending in part on the acrolein concentration, temperature and degree of damage-counteraction desired.

Where whiteness of the wool is desired, it is preferable to add to the treating solution, inaddition to the acrolein, a small amount of methacrolein. Acrolein alone in solution has some tendency to cause yellowing. In a solution containing 3 percent by weight of acrolein, the addition of about 2 percent by Weight of methacrolein reduces the tendency toward yellowing, and also prevents darkening of the wool at elevated temperatures. In this connection it has been found that the addition of formaldehyde to the acrolein solution is also effective to diminish the tendency of the wool to become yellow.

In carrying out the process the keratinous material is simply immersed in the acrolein solution, then removed and dried. The material may be rinsed prior to final drying, but this is not necessary, and when treating wool damaged by overbleaching, it is advantageous to leave the wool unrinsed and to dry at elevated temperatures such as do not cause damage to the wool, for instance, 60-120 C. or even higher for short duration.

Representative examples of the process of this invention, presented as illustrative of the best manner now known of carrying it out, and the results thereof are reported in Table II. In each example, a sample of wool was immersed in the acrolein solution, then removed, rinsed (except where noted), and dried under the conditions given in the table. Under the heading Bath Ratio is given the parts by weight of solution per part of dry wool. The pH in each example was adjusted by liili'iiihil iiUUiiii 3 adding acetic acid to the solution to lower soda ash to raise the pH.

After each treatment, the alkali solubility of the sample was determined both before and after the sample was boiled for one hour in an aqueous 0.1 N hydrochloric acid solution, and the results tabulated indicate both the degree by which the treatment improved the alkali solubility and the degree by which it stabilized the wool against subsequent acid damage. For comparison, the

the pH, or

alkali solubihty figures are also given for the samples be Example 19 fore treatment, under the heading Control. The blue dyed wool yarn reported in Table I (item 5) TABLE 11 Conditions of Treatment Drying Alkali Solubility Type oi Wool Aerolein Bath Temp., Time, 'Iemp., Bei'ore Alter Cone. Ratio pH C. M C. Acid Acid. Percent Boll Boil Control 1.....- V AustrallnnWool, 13.1 45.2

ashed and Degreased Example:

- 1 do 3 3D 3 20 20 20 8.6 19.6 2 do 0.3 100 3 20 20 100 11.7 35.2 a do 6 20 3 20 20 100 8.3 19.4 4 do 10 10 3 20 20 100 8. 3 18. 9 5 do 3 30 3 65 20 100 8. 6 16. 4 a r n 3 30 3 85 20 100 8. 8 13. 7 7 r n 3 30 3 100 20 100 7. 6 12. 8 g r n 3 30 3 20 10 100 9. 0 20. 3 u r n 3 30 3 20 60 100 7. 3 16. 0 10 r n 3 30 3 100 10 100 6.3 13. 8 11 r n 3 30 3 100 60 100 6. 5 12. 0 Control IL... Commercial Over- 47.1 74.5

bleached White Yarn. Example:

19 do 3 30 3 20 20 20 22.6 68.2 1': dn 3 30 3 20 20 100 24.8 42.5 14 n 3 30 3 100 20 100 14.3 29.2 15 -...d.0 3 30 7 100 100 13.7 26.6 m o 3 7 100 20 l 100 12. 2 23. 6

l Dried without rinsing the wool alter its removal from treeting bath.

Example 17 The peroxide bleached wool described in Table 1 (item 3) was immersed for 20 minutes in 30 times its weight of a 3% (by weight) acrolein solution (aqueous) having a pH of 3 to 20 C., then removed, rinsed and dried at 100 C. The alkali solubility of this sample was determined both before and after a 1 hour boil in a 0.1 N HCl solution.

Alkali solubility, percent Before acid boil 19.5 After acid boil 44.6

These values, it will be seen, compare favorably with the corresponding values obtained on the unbleached control, 13.1 and 45.2 respectively.

Example 18 A dyed carpet wool, having an alkali solubility of 9.9% was electrolytically stripped in a chromium sulfate solution containing 3% sulfuric acid at a temperature of 85 C., as described in Patent No. 2,549,099. The stripping raised the alkali solubility to 37.9%. The wool was then immersed in a 6% acrolein solution having a was immersed for 20 minutes in 30 times its weight of an aqueous solution having a pH of 6 and containing 3% acrolein (by weight) and 2% formaldehyde '(by weight), at a temperature of 25 C., then removed, rinsed and dried at C. The alkali solubility was found to be 8.0%. The treated yarn was then electrolytically stripped in a 5% sulfuric acid solution as described in Patent No. 2,549,099. After stripping, the alkali solubility was found to be 23.4%. From Table I it will be seen that without the a'crolein treatment the yarn, after the electrolytic strip, had an alkali solubility of 69.2%. The presence of formaldehyde in the pretreating solution substantially diminished yellowing of the yarn.

In the following example, samples of virgin Australian wool tops treated with acrolein in accordance with this invention and subsequently electrolytically stripped are compared with respect to their elongation and tensile strength characteristics, with samples of the same wool electrolytically stripped without having been treated with acrolein.

Example 20 The acrolein treatment consisted in immersing the wool in 30 times its weight of an aqueous 3% (by weight) acrolein solution having a pH of 3, for 20 minutes at room temperature, then drying at 100 C.

The electrolytic stripping process was that described in Pat. No. 2,549,099 and was carried out in an aqueous solution containing 3% (by weight) of sulfuric acid and 2% (by weight) of basic chromium sulfate.

The following results were obtained, using an Instron tensile tester, manufactured by Instron Engineering Co., Quincy, Massachusetts.

From these results it will be seen that significant improvements in the wool after an electrolytic strip may be attributed to the acrolein treatment of this invention, particularly with regard to the yield point and the breaking strength.

From the foregoing disclosure, it is apparent that the process of this invention is efifective to lessen the degradation encountered when wool is treated under acidic, oxidizing or reducing conditions, and also to counteract degradation previously caused by treatments under such conditions.

Having thus disclosed our invention and described in detail representative examples of the best manner of practicing it, we claim and desire to secure by Letters Patent:

1. The method of treating wool to reduce its alkali solubility consisting essentially of the steps of contacting the wool with an aqueous solution of between about 0.3 and by weight of acrolein and having a pH between about 2 and 7 for a time of less than 2 hours and at a temperature of less than 120 C., said time, temperature and concentration conditions being interrelated to produce a reduction in the alkali solubility of said wool, and drying said wool.

2. The method of treating wool to reduce its alkali solubility consisting essentially of the steps of contacting the wool with an aqueous solution of between about 0.3 and 10% by weight of acrolein and having a pH between about 2 and 7 for a time of less than 2 hours and at a temperature of between about C. and C., said time, temperature and concentration conditions being interrelated to produce a reduction in the alkali solubility of said wool, and drying said wool.

3. The process defined by claim 1 wherein the wool is dried at a temperature between about 60 C. and C.

4. The method of treating wool to reduce its alkali solubility consisting essentially of the steps of contact ing the wool with an aqueous solution of about 3% by weight of acrolein and about 2% by weight of material selected from the group consisting of methacrolein and formaldehyde, for a time of less than 2 hours and a temperature of less than 120 C., said time, temperature and concentration conditions being interrelated to produce a reduction in the alkali solubility of said wool, and drying said wool.

References Cited in the file of this patent UNITED STATES PATENTS 787,923 Kann Apr. 25, 1905 2,322,486 Swallen June 22, 1943 2,342,994 Atwood Feb. 29, 1944 2,383,963 Gottfried Sept. 4, 1945 2,422,586 Royer June 17, 1947 2,524,042 Croston Oct. 3, 1950 2,583,574 Jones Jan. 29, 1952 2,676,871 McGovern Apr. 27, 1954 FOREIGN PATENTS 334,528 Germany Mar. 15, 1921 482,543 Canada Apr. 15, 1952 OTHER REFERENCES Parker et a1.: J.S.D. and 0., November 1947, Protecting Dyed Animal Fibers Against Harmful Efiects of Discharging Agents, p. 362. 

1. THE METHOD OF TREATING WOOL TO REDUCE ITS ALKALI SOLUBILITY CONSISTING ESSENTIALLY OF THE STEPS OF CONTACTING THE WOOL WITH AN AQUEOUS SOLUTION OF BETWEEN ABOUT 0.3 AND 10% BY WEIGHT OF ACROLEIN AND HAVING A PH BETWEEN ABOUT 2 AND 7 FOR A TIME OF LESS THAN 2 HOURS AND AT A TEMPERATURE OF LESS THAN 120* C SAID TIME, TEMPERATURE AND CONCENTRATION CONDITIONS BEING INTERALATED TO PRODUCE A REDUCTION IN THE ALKALI SOLUBILITY OF SAID WOOL, AND DRYING SAID WOOL. 